Wireless networks, such as WPAN (Wireless Personal Area Network) systems based on IEEE802.15.4, have been deployed in recent years. Many sensor networks are developed based on WPAN technologies. Active RFID systems have also been widely used in tracking assets for the last ten years. It is appreciated that many real-life applications require a single wireless system to deliver both sensor network and RFID functionalities.
A main problem of existing wireless network systems is that it does not support a selection operation needed in typical RFID applications. Often times, an interrogator in an RFID application needs to select a portion of RFID tags to participate in specific data transactions with the interrogator. Although an interrogator can be configured with pre-selected set of RFID tags, such an approach may be too rigid for certain application. For example, the capability of a portable interrogator is severely limited without the support of selection operations.
Therefore, current wireless systems, although may be used in a sensor network application, do not provide a robust infrastructure to support RFID functionalities.